Flexible strain sensors based on MWCNTs/epoxy nanocomposite coated on a polyimide (Kapton HN) substrate are often preferred due to their outstanding properties. Nevertheless, polyimide has a poor adhesion with different classes of materials, such as ceramic, polymers and metals, caused by its hydrophobic nature and low specific surface energy. Generally, the physicochemical properties at the substrate interface are decisive for the performance of strain sensors. To enhance the adhesion to substrate, oxygen plasma cleaning is proposed as an adhesion improvement technique. For this, different exposure times were investigated; 2 min, 4 min, 5 min and 10 min. The PI surface wettability was investigated by static contact-angle measurements using two different liquids; water and n-hexane. Results demonstrate that the contact angle of water decreases with increasing the oxygen plasma treated time to reach a completely hydrophilic surface with a contact angle of 12,6° after 4 min. The effect of plasma treatment on thin film nanocomposite performance was evaluated using DC measurements. To understand the phenomena behind the increased conductivity by plasma cleaning, the chemical groups introduced by the treatment were examined using Raman spectroscopy measurements. The results show the formation of more carbonyl groups with the elimination of hydrocarbon impurities after 4 min of exposure to plasma which increase the electrical resistance.Keywords: Adhesion, contact angle, Raman spectroscopy, electrical characterization, strain sensor
© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.